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  • 1990-1994  (16)
  • 1992  (5)
  • 1991  (11)
  • 1
    Digitale Medien
    Digitale Medien
    Temperature dependence of resistivity and Hall mobility in floating zone grown bulk silicon-germanium alloys (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4341-4343 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Silicon germanium (Si1−xGex) alloys have been grown by the floating zone method with x varying from 0.5 to 20 wt %. Resistivity and Hall effect measurements have been carried out in the temperature range 80–410 K. The Hall mobility has been found to decrease with Ge concentration varying between 0.5 and 4.5 wt % and thereafter an increase has been observed. The Hall mobility has also been found to decrease with an increase in temperature in these alloys following the AT−y relation, where A is a constant and T is the temperature in K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.350817
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  • 2
    Digitale Medien
    Digitale Medien
    Ultrathin magnetic films of Fe/Ag(100): An approximate realization of a 2-d Heisenberg ferromagnet? (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5967-5967 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have measured the transmission Mossbauer spectra of Fe/Ag(100) single crystal multilayers with large thicknesses (∼100 ML) of intervening Ag as a function of both temperature and magnetic field applied perpendicular to the surface. In contrast to earlier work on samples with less silver between layers, ordering temperatures are much reduced and the initial relaxation effects observed on cooling down appear to set in with a very small or zero order parameter.1,2 Measurements with a magnetic field applied perpendicular to the film surface showed a single well defined order parameter, which rules out superparamagnetizatism as the source of the observed relaxation effects. As an example, a sample measured earlier with 2.4 ML of Fe and 4 ML of Ag exhibited a well defined order parameter in zero field with a transition temperature near 200 K. In the present case a 3.0 ML Fe sample with ∼100 ML of intervening Ag exhibited relaxation effects setting in near 100 K, with a nonzero order parameter below ∼60–70 K. Measurements in a magnetic field showed clear evidence for long range spin–spin correlations even at temperatures above 100 K. Our interpretation is that for the films with relatively thin (∼4 ML) Ag layers between the Fe, there is sufficient coupling between layers to drive an essentially 3-d magnetic transition. With a very thick Ag interlayer separation, the characteristics of the film become much more like an ideal 2-d Heisenberg model, which builds up very long range spin–spin correlations at low temperatures, but whose actual magnetic ordering transition is depressed to T=0 (finite T with anisotropy).3 Presumably the transition which we estimate to be at 60–70 K is driven by the fact that the perpendicular anisotropy is not zero, but in fact is larger than the demagnetizing field.〈ks〉
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347833
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  • 3
    Digitale Medien
    Digitale Medien
    Study of silver addition to Y1Ba2Cu3O7−y screen printed thick films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1575-1579 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A study of the effect on the superconducting and microstructural properties of YBa2Cu3O7−x screen printed thick films as a function of silver content (in the form of Ag and Ag2O) from 0 to 40 wt. % by employing different experimental techniques has been carried out. It has been found that silver improves the sinterability and intergrain connectivity and reduces the normal state resistivity. The superconducting transition temperature of the above films was found to be in the range of 82 to 91 K. Our results show that a small addition of silver (Ag or Ag2O) helps in enhancing the superconducting properties. However, large amounts lead to formation of 211 phase as the decomposed product and thereby deteriorate the quality of the superconductor. Silver has been found to remain as metal in the samples for the entire range. Further, in light of our results, it seems that an addition of Ag metal is more beneficial than the addition of Ag2O.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349520
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  • 4
    Digitale Medien
    Digitale Medien
    Bi-Sr-Ca-Cu-O superconductor with improved zero resistance temperature of 122 K (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3646-3648 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An improvement in zero resistance temperature (T0c) of the 2223 phase in the Bi-Sr-Ca-Cu-O system by using a nominal composition Bi0.8Pb0.2SrCa2Cu2Ox has been achieved. The bulk Bi0.8Pb0.2SrCaCu2Ox samples synthesized from a matrix reaction method exhibited a superconducting transition with T0c of 110 K. Addition of one Ca-atom per molecule of the above composition, that is, Bi0.8Pb0.2SrCa2Cu2Ox resulted in enhanced T0c of 122 K with onset temperature (Tonsetc) of 140 K. Interestingly, T0c of 122 K was also observed in the Pb-free BiSrCa2Cu2Ox samples, but it decreases to 115.5 K after 3–4 thermal cycles. However, no such decrease in T0c was observed in the Pb-doped samples, indicating the formation of stable 2223 phase. On the basis of x-ray diffraction, energy dispersive spectra and scanning electron microscopy data, it is concluded that excess of Ca facilitate the nucleation of 2223 phase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105607
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  • 5
    Digitale Medien
    Digitale Medien
    Studies on Marine Chemicals, Part IV. Isolation of Cholesterol Derivatives from the Marine Sponge Spirastrella inconstans (1992)
    s.l. : American Chemical Society
    Journal of natural products 55 (1992), S. 1310-1312 
    Details
    ISSN: 1520-6025
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/np50087a021
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  • 6
    Digitale Medien
    Digitale Medien
    Prognosis in contre-coup intracranial haematomas — a clinical and radiological study of 63 patients (1991)
    Springer
    Acta neurochirurgica 108 (1991), S. 30-33 
    Details
    ISSN: 0942-0940
    Schlagwort(e): Head trauma ; contre-coup injury ; CT ; prognosis ; traumatic cerebral haemorrhage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The clinical and radiological prÒfiles of 63 patients with contrecoup haematomas were studied. The overall mortality was 53%. The mortality in patients with contre-coup haematomas alone was only half of that found in patients with associated coup injury (80%).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01407663
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  • 7
    Digitale Medien
    Digitale Medien
    Cytogenetic studies on MIC gas-exposed persons in Bhopal (1991)
    Springer
    Human genetics 〈Berlin〉 87 (1991), S. 513-515 
    Details
    ISSN: 1432-1203
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00197181
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  • 8
    Digitale Medien
    Digitale Medien
    Cytogenetic studies in leprosy patients before and after chemotherapy (1991)
    Springer
    Human genetics 〈Berlin〉 87 (1991), S. 665-670 
    Details
    ISSN: 1432-1203
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The frequencies of chromosome aberrations and sister chromatid exchanges (SCEs), cell proliferation kinetics and mitotic indices were studied in peripheral blood lymphocyte cultures of leprosy patients both before and after chemotherapy. The differences in the frequencies of chromosome aberrations and SCEs between controls, paucibacillary and multibacillary patients were found to be statistically highly significant (P 〈 0.001). The extent of cytogenetic damage seemed to depend on the severity of the disease. Lymphocytes of untreated leprosy patients showed a low mitotic index and a slow rate of cell proliferation. Following combined treatment with dapsone and rifampicin there was an increase, but to a lesser degree (P 〈 0.01), in the frequency of SCEs and chromosome aberrations while the drug combination of dapsone, rifampicin and clofazamine had a non-mutagenic effect on chromosomes of the patient. Furthermore, after drug treatment, the cell proliferation rate and mitotic indices in paucibacillary patients were comparable to that of controls. These results indicate the clastogenic potency of Mycobacterium leprae and the remedial effects that follow therapeutic drug treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00201722
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  • 9
    Digitale Medien
    Digitale Medien
    Photoconduction in sintered cadmium sulphide pellets at elevated temperatures (1991)
    Springer
    Journal of materials science 10 (1991), S. 1299-1300 
    Details
    ISSN: 1573-4811
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00722640
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  • 10
    Digitale Medien
    Digitale Medien
    Interference effect of two closely-spaced shallow strip foundations on geogrid-reinforced sand (1992)
    Springer
    Geotechnical and geological engineering 10 (1992), S. 257-271 
    Details
    ISSN: 1573-1529
    Schlagwort(e): Geogrid ; group efficiency ; sand ; strip foundation ; ultimate bearing capacity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Summary Geotextiles and geogrids are now being used extensively in many civil engineering construction works. This study presents some laboratory model test results for the ultimate bearing capacity of an isolated, and two closely-spaced, strip foundations resting on unreinforced sand, and sand reinforced with layers of geogrid. Based on the model test results, the variation of the group efficiency with the centre-to-centre spacing of the foundation has been determined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00880704
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